Selective telegraph station calling system



J- L. MAXWELL SELECTIVE TELEGRAPH STATION CALLING SYSTEM July '26, 1949.

Filed 001;. 29, 1948 INVEN TOR JOHN L. MAXWELL lavish ATTORNEY.

pulses willibe understood to mean the significant marking and spacing pulses which determine the letter to be printed by the teletypewriters receiving the signal, or the function to be performed by the teletypewriters. Code pulses will be understood to exclude the start pulse and the stop pulse. In the usual tape transmitter the total number of code pulses is the same in each group of pulses. Thus there may be five' code pulses, any one of which may be either marking or spacing. The expression codejinterval will be understood to mean the time interval during which the code pulses of one group of pulses are transmitted. Thus if each group of pulses includes a start pulse, five code pulses and a stop pulse, a code interval is the time interval during which the five code pulses aretransmitted.

4 lay H, in respoiis to signals received from other stations, or from the transmitter of station C, controls a teletypewriter [3 which includes means for printing the received messages. The tele-, typewriter may conveniently be of the general type described in Patent No. 1,904,164, granted April 18, 1933, to SterlingMortonet al. A keyboard perforator l4 periorates tape in accordance with messages to be transmitted and feeds it to a tape-transmitter including a tape-sensing mechanism and a distributor. Th tape-transmitter may be of the general type described in Patent No. 2,055,567, granted September 29, 1936, to E. F. Watson. Usually the tape transmitter will beemployed to transmit messages, but under some circumstances it may be desired to transmit In one embodiment of the invention there is binations of marking and spacing code pulses including the blank or all-spacing combination, switching means connected to suppress said stop pulses, a switch actuator, and means for applying said code pulses to the switch actuator The switch actuator is adapted to actuate the switching means in a direction to suppress the stop pulses in response to successive blank code combinations, or more particularly, response to successive code combinations including a continuous interval devoid of marking code pulses, said interval being of greater duration than a predetermined value. During ordinary transmission of messages there will occur relatively short intervals devoid of marking code pulses; for example, there may occur, in'succession, code combinations such that the latter part of the codeinterval of the first code combination is blank, and the early part of "the code interval of the succeeding code combination is blank. "In order that the switch actuator mentioned above may not interrupt the stop pulses during ordinary trans-.

mission of messages, the predetermined value of the time interval to which it responds should be greater than any interval between marking code pulses which would normally occur during ordinary transmission of messages.

The above mentioned, as well as other objects, together with the many advantages obtainable by the practice of the present invention, will be readily comprehended by persons skilled in the art by reference to the following detailed description taken in connection with the annexed drawing which respectively describes andillustrates a preferred embodiment of "the invention.

There is illustrated in the single drawing a telegraph system including a plurality of serially connected stations such as A, B, C, D and E. Station C is represented by the main body of the drawing. Stations A, B, D and E may be considered to include identical elements corresponding to those which will be described in connection with station C.

Referring now to the drawing, it will be observed that in this illustrative embodiment ,the various stations are inter-connected, in series, by a line conductor l a, current being supplied to the line at one end by a battery ll having its negative terminal grounded. The opposite end of the line, near station is shown as grounded, thereby completing a series circuit. Each of the stations in the illustrative system includes receiving means and transmitting means. At station C a line remessages from a manually operated keyboard transmitter, and there is therefore provided a keyboard transmitter l6 as a part of the teletypewriter l3.

At each station there are provided circuit means including relays I1, I8, I9 and 20 which,

in response to certain receivedsignals, cooperate to activate or deactivate the perform other functions. p

The tape transmitter and its associated elements will be described in detail at a later point, but in order to explain the probi em of suppressing the stop pulse and the advantage of suppressing this pulse, the operation of the transmitter which produces this pulse Will be briefly stated at this point. The tape transmitter comprises a distributor 2| adapted'to open the line, thereby producing a spacing pulse, or to complete a cir cuit for the line, thereby producing a marking pulse. The distributor 2| has, in the illustrative embodiment, stop pulse segment, a start pulse segment, five code pulse segments 1-5, and a brush arm 22 which rotates past these segments.

One side of the line is constantly connected to the distributor brush arm. The start segment is an open eircuited segment, with the result that a spacing pulse is transmitted each time the arm rotates past this segment. Interposed between each of the five code pulse segments and the line is switching means operated by sensing members controlled by the perforated tape. Thus as the commutator arm rotates past the five code segments, a combination of marking or spacing pulses will be transmitted to the line, depending upon the combination of perforated and blankareas present at that instant on the portion of the tape being sensed. In tape transmitters prior to the present invention, the connections between the stop segment and the linehave been such that a marking pulse was transmitted by the tape transmitter every time the distributor arm rotated past the stopsegment, regardless of what code combinations were fed into thetransmitter on the tape. Thus upon receipt ofa stretch of blank, tape, the transmitter would repeatedly transmit a spacing start pulse, a series of spacing code pulses, and a marking stop pulse.

The present invention provides means associated with the tape transmitter forfsuppressing the stop pulse when a blank length of tape is Such means causestuting a. second group of called stations for a first group of called stations, it may be seen that the present invention is a significant advance 7 receiver and to animate in: the art, bccauseina telegraph: system: embodying: the present; invention: atape transmitter sup'- pliedwithi properly perforated tape? may: set up callsto successive groups of: stationspexcluding other:stationsalliwithoutmanual aidi In; additionv to the previously mentioned ap-- paratus',. there is. prov-idedwat-each:station a manually operable break" key" 23.. When this key; is depressed; the. line.- circuit is opened; and: the key is of the slow-return type in order tdpro v-idea timedelay before the'key again closes the circuit. Means. for producing such a delay-areschematically illustrated asia da-shpotiim, Among. other uses; thekey 2 3 is usctul in'= sendlng a break signal: to the line preparatory to settin mpwa calib means of; the keyboard transmitten l,6..- If the tape transmitter were goingused, the long break; whichv turnson all stations; could :besent merely by, causin the keyboard perforatorto; supply the tape; transmitten with a: series of? blank. code combinations.

The system: will now be: described in. more detail in; connection with 1 a description of theoperation of: setting; upra-callr. The operation of the relays. ils-28,. in: connection with the teletype writerl;3, in response to signals received by the: linerelay t2; will firstbedescribed;

Setting-up. a call Initially, when the line is idle, it is in a markin'gicondition, thatis, it is energized. The-motors oi' all teletypewriters are stopped. The sequence of transmitted signals for setting up a call will now be summarized, and their the response of the system to such signals will be described.

First, a longbreak signal is sent to the line. 'I h-ismay be accomplished either by a break key such as 23, or by a tape transmitter. The longv break turns on the motors of all telctypcwriters and hasother effects.

Second; there is then transmitted to the line a sequence of threecode combinations, namely;

Figs, Blank, and a letter corresponding to thestationcalled; Thus-if one wishescto call in station C, one would transmit Figs-Blank-C.

Additional stations may also. be called in,.so that.

theyall m'ay receive thesame message. Among. the receivers usually called in is the receiver at the transmitting: station, for the reason that it Thissequencc turns off the teletypewriter motors. at: all uncalled stations, excluding them from. the; call. In designing the system the letter S isarbitrarily chosen for this disconnect function. Another letter could have been used instead.

The operation of the system in response totsuch signals will. now be described in more detail;

The line relay l'2, which. is of. the polarized type, is] provided with-a single contactiitowhich its-armature is. driven when the upper winding of therelay, which is in. seriesiwith. the. line,, is;

To call in stations C, D. and E, oneenergized D-hereiisiprovided'subattery3llhaving one tcrminaltgrounded anci having its other terminal connected through a current limiting: resistor 31 to the armature of the relay. l2. The lower or biasing: winding. of the relay; is connected: in= aserie's circuitrwith a battery. stand a current limiting resistor: 33.. The action of thiswlow en windingin response to: current supplied-from the battery32, istourge the armature ofi-the relay t2 toward the left, that is, in' the spacing direction. Hence whenever the lililea M is opened; the: armature. of the relay will; movev to the left, away from its marking. contact 2 5"; into: a; spacing position, thereby disconnecting the battery 35% from: the contact of the relay; Normallmwvheni the liners idle, that. is, when-no messages: are: being transmitted by any station, thelinais energized, and thearmature of "the: relay lz is. in the marking position, against its; contact.

When-theline is in an idle condition; therelayr I1 is energized: through-a. circuit leading.- from battery. 3G,,through-resistor 3l,armature of the relay l2; contact 25,:lcad 34; outer upper armature. front contact of the relay l1, arm; 35: and associated: contact of switch. 36, to vvindingi of. relay M. The relay I9 is: energized and: the. relays I8 andZ-(L are deener-gized when" the line is--:in. anr id-lecondition. @perating oircuits fori theserelay-s will be described subsequently.

Upontoccurrence'ofa: long break signal, the:

line relay. l2.- moves toaasspacing position and deenergizes the relay H by opening the previously described circuit at. the contact. 25* oi the line: relay;- lZt.

. All. relays: in the illustrative system; with: the: exception. of the line relay I 2:, are provided! suitable-spring. means for urging their armatures: in. a. direction away from; their pole faces, thatwis; away from. their frontcontacts and toward their" backeontacts. Thisspring meansymay comprise: aportion ot the. armature'itselfh l'fhe line relay! t2; hasbeen. described as employing a biasing winding for performing the function approximately equivalent to. that performed by the springmeans ofthe other relays.

Therel-ay t1: isof the slow-release type. It's releaseltime is sufliciently great that the relay will v not releaseadurings spacing intervals occurring during normal transmission of messages. Such spacing, intervals may,.in some systems, be of. the. order of: one-thirdi of a second, but in order to provide a margin of'safety against hits, the release time of the relay I'! might be approximately 3: seconds. Upon" the" release of the relay. t'htheengagement of its inner upper armature with. its back contact completes a circuit from a battery 3Jrt'0f energize a motor controlrelay,- 38., Iniseriesl with the battery 3Tis a currentlimiting'resistor; .S-imilar resistors are connectedtini series with other batteries of the sys-- tem, and, for-simplicity; will not be mentioned specifically. When.- the relay 38 is energized, its armature closesaa circuit to supplycurrent from a current source 39 toj=a=motor 40 of the teletypewriter |3a In this manner the motors are started at all stations: whenalongbreak is sent to the line.

Release of theouter upper armature of the relay H connects the selector magnet 4 of the teletypewriter through the-back contact of this ar-maturetc thejsconta'ct 25 of the line relay l2. Hence. sinccrthe IIlOtOIlfllof the teletypewriter' is. now running and: since. selector magnet 41 is newresponsive?torsignalsun:the line, the telestypewriter I3. is responsive to line signals. This same condition will exist at all stations.

Prior to the transmission of the long break signal, when the line was idle and the relay I] was energized, the relay I9 was held energized through a. locking circuit including a battery 43, the winding of the relay. l9, front contact and lower armature of this relay, inner lower armature and front contact of the relay 11, to ground. When the relay ll releases in response to a long break signal in the line, as explained above, the locking circuit for the relay l9 will be broken at the inner lower armature of the relay l1, and the relay I9 will therefore release. There is provided a lamp which, when lighted, serves to indicate that the line is busy. When the relay I9 is released by the relay I! in the process of setting up a call, current is supplied to the lamp from a battery 44, through the back contact and inner upper armature of the relay l9. The lamp remains lighted until the call is terminated and the line is returned to an idle condition.

The teletypewriter l3 at station is provided with a function lever 42 and is adapted to move this lever upward only in response to receipt of signals comprising in sequence, the code combinations Figs-Blank-C. The corresponding function lever on the teletypewriter at station D is responsive only to the sequence Figs-Blank D. For an explanation of a system adapted tothrough a circuit including a battery 41, outer upper armature and back contact of the relay !9, a switch 50, upper armature and front contact of the relay 20, the winding of this relay to ground, The momentary closing of the switch 45 by the function lever 42 also energizes the relay l8 by connecting its winding to the battery 46. The relays 8 and are purposely chosen so that relay 20 operates slightly faster than does relay l8, in order that the relay 20 may look up before the outer upper armature of the relay l8 disengages its back contact and thereby breaks the circuit from the battery 46 to the relay 29. It will be understood that the lever 42,,while operated upwardly only momentarily, will remain in the operated position long enough for both the relays l8 and 20 to operate.

' Returning now to the action of the relay t8 following the momentary closing of the switch 45 by the lever 42, it may be noted that the relay I8 locks up through a locking circuit including its winding, front contact and lower armature back contact and outer upper armature of the relay l9, and the battery 41.

It will therefore be seen that at this stage, the result of the transmission of a sequence of code combinations including Figs-Blank" and a letter indicating the called station, is that the relay I8 is energized at the called station or stations and is not energized at the other stations. The inner upper armature of the relay I8 is therefore out of engagement with its back contact at the called stations. It will be seen in a moment that the significance of'this fact is that .8 the transmission of a sequence of code combinations which actuates a function lever 5| will have no eifect at the called stations, but will have the effect at all other stations of stopping the motor 45 of the teletypewriter and disconnecting the selector magnet 4|. Another difference between the conditions at the present stage at called and uncalled stations is that at called stations the relay 20 is energized, while at uncalled stations it is de-energized.

The energization of the relay 20 at the called stations completes a circuit for a buzzer or bell '52, including the battery 31, the inner upper armature of the relay ll, which is now engaging its backcontact, the buzzer 52, and the lower armature and front contact of the relay '20, to ground. -When the buzzer or bell 52 is energized, the operator at the receiving station is thereby informed that the station is about to receive a message. by temporarily opening the switch 59, thereby breaking the locking circuit for the relay 2!].

In order to turn off the teletypewriter at uncalled station-s, the transmitting station now transmits to the line a sequence of code combinations which will actuate the lever 5|, momentarily moving this lever into an up position, thereby closing the contacts of a switch 53 controlled by this lever. The identical code combination controls the lever 5| at all stations, by means generally similar to that described in the previously mentioned Morton et a1. Patent No. 1,904,164. In the illustration the sequence of code combinations chosen is Figs-S. It might satisfactorily be other sequences, such as, for example, Figs-A or Figs-Z. As was previously stated, the operation of the lever 5| and the momentary closing of the contacts of the switch 53 has no significant effect at the stations which have been called by the previously-described actuation of the lever 42, because the circuit including the contacts of the switch 53 is open at the inner upper armature of the relay [8, this relay having been energized at the called stations. At uncalled stations, however, the operation of the lever 5| serves to turn off the teletypewriters, in a manner now to be described. At those stations'the momentary closing of the switch 53 energizes the relay l'l through a circuit including the battery 54, the switch 53, the inner upper armature and back contact of the relay l8 (this relay being de-energized at uncalled stations), the switch arm 35, its contact, and the winding of the relay H, to ground. This energizing cirr cuit for the relay H is closed only temporarily by the function lever 5|, but the relay l'l locks up at all uncalled stations through a locking circuit including the battery 30, armature and con-v because, as stated, the relay H is of the slow-release type, and will release only on a long break signal on the line. It is therefore seen that as a result of the transmission of the Figs-S signal, the relay I1 is operated at uncalled stations, but remains in a de-energized condition at called stations. When the relay I! is energized at the uncalled stations, the energizing circuit for the motor control relay 38 is broken at the back contact and inner upper armature of the relay I1.

Also, the selector magnet 4| at the uncalled sta- The operator turns off the buzzer 52 tions.

their motors "and connecttheirselector magnets tofthe-contact of 'th'eline'relay I2.

Means are provided for 'short-circuiting the keyboard transmitters Hi at uncalled stations, thereby preventing the transmission of messages by such keyboard transmitters. This short-circuiting function is performed by the outer-lower "armature and frontcontactof the relay l'l,which are connected across the terminals "of the keyboard'transmitter 1'6. Sincethe'relay I1 is energized at uncalled stations, the keyboard transmitters at 'these stations are short-circu'ited.

Terminating-a call In order to terminate a call, two steps are taken. First, a long break signal is transmitted. I

plained .at a previous point, such a break signal produces this effect "by opening the locking circuitfortherelay IT at the contact 25 of the line relay "1'2 foralong enough time so that the slowrelease relay [1 will release. When this relay releases, its locking circuit is "broken at its outer upper .armatureand front contact. 'The release of the relay 'l'l connects the selector magnet 4| through the outer upper armature and back contact of the relay I! 'to the marking contact 25 of'the line relay I2, softhat the selector magnet and hence the teletypewriter is responsive to signals in the line. The release of the relay I1 also turns on the .motor '40 by completin a circuit from battery 31 through the inner upper armature and back contactof the relay l1 and the winding o'iithe relay 38 to .ground. When the relay 38 isrnergized, the motor 'is connected to its power supply39.

At the :present stage, at an stations, the teletypewriters are on and relays ll, 19 and '20 are released. The relay 18 is on at the .previously called stations but off at the previously uncalled stations. The busy lampisstill on.

The second step in terminating 'a call is the transmission of "such a'sequence of cod'ecombinations as will actuate 'a function lever 55 at all stations. In the illustrative system, the teletypewriters at all stations are adapted "to .actur ate their respective lever 55 "in response to the successive code combinations Figs-G? In this respect they are generally similar to the system described 'in Patent 1,904,164. The lever "55 momentarily moves upwardly, thereby momentarlly closing a switch "56 and energizing the relays M and i9 "throug' lra path including the bat tery "43, the winding of the relay 19; alead 58, a lead 59, the switch 56, and the winding -of the relay 11, to ground. The relay H "locks up through its locking circuit previously described,

namely, battery 30, armature and marking contact of the line relay t2, outer upper armature and front :con'ta'ct of the relay =l'l, switch arm 3-5 and its contact, and winding- "of *relay Fl, tcground. l

The relay I 9 locks up through a circuitlinclud ing the battery 4,3, the winding of therelay 19, its front contact and lower armature, the .inner .lower armature and front contact of the relay "I I, to ground. Theoperation and the looking of the relays 'l! stops all the teletypewriter motors and disconnects their selector magnets 41 from thecontact "25 of the line relay. .The operation of the relay 19 .turns off the. busy lamp. Corresponding relays, of all stationsrare now in the same condition.

hocally activating teletypewriter at am excluded station -It may sometimes occur that the operatorsof an uncalled station desires to monitor the :sig- .nals being transmitted between :other stations, in order that he may ascertain their importance relative to a message which hehimself :may 7016+ sire to transmit. .It is therefore advantageous for the operator of ran;uncalled 1 station :tobe aible to cause his teletypewriter to be temporarily responsive to the signals being transmitted. u'l'fo perform this operation, the operator at the amcalled station :in question :opens "the icontactsrof the switch arm 35 by turning :the control @arm into an upposition momentarily, for ani ine terval sufficient to cause the slow-release relay I -to release. The release -:of this (relay .I'BSlllbS from the fact that its locking path through :the switch arm 35 .is broken. The effect on the relay i1 is the same as the transmission =of a long break. .That is, when the :relay it! releases, fit turns on the 'teletypewriter motor 40 (and causes the teletypewriter selector magnet 41 to @be responsive to line signals.

.After having monitored the messages for a while, the localwoperator may turn off his teletypewriter by temporarily rotating the control arm 6.0 .into a clown position, thereby :causing'the switch arm 6| momentarily to engage its acontact. This action completes the energizing-circuitof relay ll through a path including the battery 51, the switch warm 6| and its contact, and the winding of the relay l1, to-ground. The relay H there-upon locks up through its previously described locking-circuit :irom battery 3|] and remains locked up, despite operation of the line relay -12 in response to normal "messages, since it is of the slow-release type. None of the relays l8, 4:9 and 2|] has "been affectedby the operation of switch arms 35 and N, because relays i8 and 20 are energizable only through switch 45 and relay dais energizable only through switch '56.

Transmitter "Tape transmitters per se are known heretofore. For 'a description of a typical tape transmitter reference maybe made to Patent No. 2;(l55;567,granted September 29, 1936, to E. F. Watson. Such tape transmitters receive periorated tape, which has been prepared in a repe -forator or keyboard perforator, and depending upon the positionso'f combinations of perforatedan'd unperforatedregions in the tape, the tape transmitter transmits to the line various code combinations. The code combinations normally include a start pulse which is a spacing pulse, -five code pulses which may be various combinations -'of marking 01" spacing pulses, depending upon the perforations of the tape, and a stop pulse which is a marking pulse. As previously mentioned, "in tape transmitters prior to the present invention, the marking stop pulse 11 has been necessarily transmitted for each code combination/ More particularly, even if the tape is entirely blank, that is, even if it"includes no code perforations, the stop pulse would still be transmitted at the end of' each code combination. It has already been explained why it is desirable for the tape transmitter to be capable of transmitting a long break or spacing pulse to the line, suppressing the stop pulse completely for the transmission of a long break, but transmitting the stop pulse in the usual manner when ordinary code combinations are sent. Thus with a system including receiver-controlling means of the type described, and stop-pulse-suppressing means, if a station desires to transmit a message to; a first station or group of stations and then to transmit another message to a second station or group of stations, it is possible to perforate a strip of tape in such a way that the tape transmitter would call in the first station or group of stations, transmit the desired message, deactivate those stations, call me second station or group of stations, transmit the desired] message, repeat the operations until all desired messages have been sent, and thereafter deactivate all stations, all without manual assistance from the operator. In a system including means at the receiver of the type illustrated adapted to control the receiver as described in response to a series of control signals, the transmission of a long break signal is necessary in order to call up stations which have previously been disconnected from the line. It is recalled that such stations are called up in the process of terminating a call. Also, a long break signal is necessary to call up all stations in setting up a call. In order to produce such a long break signal, the tape transmitterto be described includes means which cause the tape transmitter to suppress the stop pulse in response to the appearance of a stretch of tape blank of code perforations.

As shown in the drawing, the tape transmitter, which was briefly described at a previous point, includes a distributor having a solid inner distributor ring 62 and a segmented outer distributor 'ring, both of which are suitably attached to the upper surface of an insulating disc not shown. The outer distributor ring is divided into seven segments insulated from one another, which include a stop segment, a start segment, and five code pulse segments, numbered l-B in thedrawing. The stop se ment is, in one embodiment, longer than the other segments. Thus the other segments may be of equal length and the stop segment may be approximately 1.4 times as long as one of the other segments. The distributor brush arm 22 continuously engages the inner ring 62,. and successively engages segments of the outer ring with a Wiping movement. Connected to the respective segments I-5 are five contacts .63. There are provided five contact arms 64, associated respectively with the contacts 63. In order to sense the'perforations in the tape l5 which is fed to the tape transmitter by the keyboard perforator [4, there are provided five sensing pins, one for each of the five contact arms 64, and mechanical linkages from each sensing pin to its contact arm for controlling same. Such sensing pins and linkages are disclosed in the above-mentioned Watson Patent No. 2,055,567, granted September 29, 1936, to which reference is made for more complete de-. tails. The contact arms 64 in the drawing of the present application may be considered to represent schematically the entire means which senses the perforations of the tape and which establishes contact between a lead 65, common to the contact arms,.and contacts 63 selected in response to the code perforations. The arrangement is such that when a sensing'pin engages a hole in the tape, the arm 64 controlled by that sensing pin engages its contact 63. The tape I5 is provided with a series of feed holes arranged approximately along t e center line of the tape by which it is intermit tently advanced by the tape transmitter.

The distributor brush arm 22 is carried by a shaft 70 which is driven by a motor H through a friction clutch l2, and a worm gear drive 13. The motor H is supplied with current from'a current source 74 through a manually operable control switch 15. s

In normal operation of the transmitter, it occurs frequently thatthere is a difference between the rate at which the transmitter operates and that at which the tape is fed from the perforator to the transmitter. It may be'seen that if the perforator operation is interrupted, the transmitter will use up all the slack in the tape and would thereafter proceed to damage the feed holes in the tape unless provision were made to stop the transmitter automatically. For the purpose of taking care of the diiference between the rates of operation of the transmitter and the perforator, there is fixedly mounted on the main drive shaft 10 a stop cam is formed with a peripheral shoulder 16a. Associated with the stop cam is a stop arm 11 pivoted at E8 intermediate its ends to a frame member, not shown, one end of the arm 11 being urged to engage the periphery of the stop cam by a spring '59. The opposite end of the stop arm TI is operatively associated witha magnet which is employed to rotate the stop arm about its pivot to move it out of engagement with the stop cam periphery when the distributor is to rotate. The magnet 80 is connected in a series circuit with a battery 8|, the winding of a relay 82, a contact 83,-a contact arm 84 and a manually operable switch 85, to ground. The arm 84 and the manually operable switch 85 each are adapted to open 1 the series circuit. The arm 84 is controlled by an the contact arm 84 engages the contact 83. Before the tape transmitter is turned on for transmitting messages, both the manually operable switch 15 and the manually operable switch 85 will be open. In starting up the transmitter, the switch 15 is first closed. The motor H will then rotate, but the arm T! will prevent rotation of the distributor shaft 18. The friction clutch 12 will allow movement of the motor shaft despite the fact that the shaft It and worm drive 13 are stationary. When, as the next step, themanually operable switch85 is then closed, current from the battery 8| energizes the magnet 83, which attracts the left-hand end of the arm 11, causing this arm to pivot in a clockwise direction, thereby releasing the stop cam 76.. The distributor then rotates. If the keyboard perforator should stop. or lag behind the distributor, the tape l5 would become taut, thereby through the action of the stop lever 86 opening the energizing circuit for the magnet 80 at the contact 83. When the magnet 80 is de-energized, the arm 71 engages the shoulder 16a of the cam 16, preventing rotation of the distributor. The motor may continue to rotate because itis coupled to the transmitter through the friction clutch l2.

.18 Meanaintransmitter for suppressing stop pulse The circuit including thestop segment may be traced from the line to at the break key =23, through the 'keyboard transmitter I S, through the lead 8 to the inner ring 62 of the distributor, through the brush arm the stop segment, lead 8B, armature and front contact of a-rel'ay 8-9, a lead 90, and out the line ill. "It will be notedthat thiscircuit does not include thecontacts 453 and the arms 6 It will also b'e noted that the stop pulse can be transmitted only when the relay 89 is energ ized. This relay is of the slow-release type. Current to its winding is supplied from a battery 51 through the front contac't-and armature of a relay iii or through the armature and back contact of a relay '82. Thus whenever the relay U2 is energized or the relay 82 is released, the winding of the relay "39 is energized.

The winding of the relay "92 is connected in series with the contacts 63, the contact arms =34, thelead 65, and the "line 10. It may therefore be seen that the winding of 'the rela 9-2 will receive a pulse of current each timea markingpulse is transmitted to the line throughone of the segments 2, '3, 4, or The relay 89 in 'turn receives a pulse of "current each time the relay 92 is energized, and therefore the relay 89 will be energized at least once during any revolution of the distributor corresponding to a code combination on the tape having any code perforations whatsoever. The release time of theslow-release relay w is greater than the greatest interval normally occurring between marking code pulses during "transmission "of ordinary signals. As long as a series of code combinations other than blanks is being transmitted, the armature of the relaydB will remain continuously inen-gagement with its from contact, and a stop pulse will be transmitted each revolution of the distributor.

Ii, however, there appears-on the tape a'blan-k stretch, that is, a length free from code perforations, the relay92 will not be energized fora period corresponding to this blank stretchof ta-pe, since code :pulses will not appear in the lead 6'5, inasmuch as all thearms B l-will be out'ofengagement withtheir contacts. Provided'the period is long enough, the slow-release relay 89 will release. .As long as the armature of theslow-release :relaydQis out of engagement "with its contact, revolution of the distributor arm over the stoprsegment will not produce a stop pulse, since as Epreviously mentioned, the stop pulse annot be transmitted to the .line when theirelay ufl is in a released condition. It may therefore :be seen that thesrelays .92 land 89 cooperate .to produce a long, continuous break :or spacing condition on therline in response-to a "stretch of blank ttape .being :ied from the :keyboard ;-perforator to the tape transmitter. The desirability of suchoperatio has beenpreviously explained. i

It may be seen that. if the distributor ziszstopped for any length of time, .the slow-release-relayiifl would tend to release, since there would ben'o code pulses to energize .it via the relay. .92., :ii?

means were not provided to prevent the release:

of the relay 8.9 when the distributor isstopped. The reason that the released therelay -89 isun desirable whenthe distributor is stopped is that the 'brusharm 22 will :then be engaging the-stop segment, and the release of the relay 8.9 would open-circuit the line, preventing other stations from transmitting. For the purpose of preventingtherelease of the relay 89 when the distnibutor is stopped, the armatureand backcontact-nf 114 the molar :82 are connected in paral'iel Withdlhfi armatureand front contact of the relay :52. Hence, when released, the relay:8.2 :provides weir-- cuit torthe energizationaof:relay flS.

Whenever the distributor is rotating, the relay -82 energized, since its. winding is in series with themagnet 8'0. 'WhiChTCOIItlOIS rotationiof the dis: tributor. 'Ilherefore when the distributor is retating, the armature :ofithe relay 812 will be out of engagement with :its back contact, and the relay 82 will not afiectrthe relay- 89.

When thedistnibutor is stopped by the :operatorfs opening the switch 85 or by the taut tape lifting the arm-84 away from'the contact 83, the energizing circuit for the relay &2 is opened. The release of the relay -82 provides an energizing path from the battery 9| by-passing the relay 92 to the winding of the relay 89.. The :relay :89 is thus maintained energized while the distributor is stopped, thereby -providing a circuit from the line it] through ithe stop segment, as desired.

:It has been stated previously that the release time of the slow-release relay e89 should be. greater than the longest interval normally occur ring between code pulses of marking nature rdlflingetransmissionef ordinary signals. This .-is true because the armature of the relay 289 should l'emainagainst its irontcontact, to permittransmission of the stop pulse, at all times except when a blank Stretch-Hf tapeis fed intothetna-nsmitter. It will be u-nderstood thatthe term -code pulses of marking nature refers only to pulses which have selectiveattributes, and excludes the stop pulses, which-are alsoef marking nature, but

do not enter into selective operations.

With the usual sin-odes -ofoperation of the tape trensmtiters (of the type previously-described, the greatest interval between marking code pulses during 'transmission of ordinary message signals would ,occur when ithere appeared in sequence a first (and aesecond .eode combination such that only the first pulse of the first code combination and the last pulse'of the second code combination is marking, .all intervening code pulses being spacing, :More ,particularly, in a tape transmitter havingfive ,code lsegments such as that i1- lustrated, the longest interval would occur when there appeared von the tape :two consecutive code combinations, .the .fiI'St code combination being adapted 'to position the contact arms 64 so that a marking code pulse is transmitted through only the'inumber I segment, and the second code combination being adapted to position the contact arms lifl so that a marking code pulse is transmitted through only the number 5 segment. As a result there would appear an interval devoid of marking code-pulses represented by the time required for the distributor brush to "rotate one complete revolution, plus the distance from the trailing edge of "the 'number I segment to the leading edge er the number 5 segment. Therefore in a system having a tape transmitter of the general type shown in the drawing, the release Ztime of the slow-release relay 89 should re at least equal to approximately the period of one complete revolution of the distributor brush, plus the interval required forthe brush to travel from the end :of :ther'fntst code "segment to the beginning ofiaherlast'codesegment.

It :may therefore be .seen that @the release time of the slow-release relay 89 may satisfactorilyibe abn'ut twice the time required :for acne revolution of the distributor, or greater.

. The apparatus which-suppresses the stop pulse may in :someembodirnents be referred to as scum? prisingaitimer. In thecircuit'of the attached drawing the timer may be considered to comprise'the apparatus within the rectangle designated by the reference numeral 93. From the previous description it will be understood that the distributor and the tape sensing mechanism of the tape transmitter are adapted to generate marking stop pulses at a terminal 94 and marking and spacing code pulses at a terminal 95. The line It] leading to station D, and other portions of the line circuit may be referred to as a transmission circuit. The circuit from stop pulse terminal 94, through the armature and front contact of the slow-release'relay89 and the lead 90 tothe line NJ may be termed a stop pulse output circuit, and the circuit from the code pulse terminal 95 to the line It may be termed a code pulse output circuit.

In one manner of describing the present invention, it may be stated that there are provided switch means for suppressing the code pulses, such as the armature and front'contact of the slow-release relay 89, and an actuator for controlling the switch means. In the illustrative embodiment the armature of the relay 89 is controlled by the winding of that relay, which in turn is controlled by the relay 92. Means associated with the armature of the relay 89, such as spring means, are provided for urging this armature away from its front contact.

Assuming that the slow-release relay 89 is released, the winding of this relay, together with the relay 92 which controls this winding, is adapted upon the occurrence of one or a series of marking code pulses at the terminal 95, to move the armature of the relay 89 into a position to allow transmission of. the stop pulse and to hold the armature in that position for a definite period of time following each markin code pulse or following the last of the series of such pulses. Thus the actuator has a delay or timing characteristic. It will be understood that although the timer may advantageously employ a slow-release relay to obtain the desired delay, the timer might employ an actuator comprising an electrical circuit including means for charging or discharging a condenser in order to obtain the desired delay or might employ mechanical delay means.

The timer, or the actuator thereof, will be observed to be responsive to a characteristic of the composite signal generated by the transmitter and appearing at the terminals 94 and 95. Thus if the composite signal is a series of successive code combinations each comprising a spacing start pulse, one or more marking code pulses, and a marking stop pulse, the timerwill hold the armature of the relay 89 against its front contact as long as the composite signal has .such a wave shape. If the Wave shape of the composite signal now changes so that there is applied to the timer a plurality of successive code combinations comprising a spacing start pulse, five spacing code pulses, and a marking stop pulse, the actu-' ator will respond to this new wave shape by moving the armature of the relay 89 into a released position, thereby suppressing the stop pulses. Thus since the actuator responds difierently to, or discriminates between, different wave shapes, it may be referred to as comprising a wave shape discriminator.

Also, the actuator may be viewed as responsive to the repetition frequency of the marking code pulses, since it allows the stop pulses to be transmitted only when the marking code pulses are repeatedat intervals no greater than a predetermined definite value.

The actuator may also be described as responsive to repeated occurrences of a predetermined code combination. Thus in response to a series of blank code combinations, the actuator is adapted to move the switching means in a direction to suppress the stop pulse.

In conclusion, it may be observed that there has been disclosed, in a telegraph system, apparatus associated with a transmitter, adapted to transmit a continuous break signal inresponse to a blank stretch of the tape.

Although a particular embodiment of the invention has been shown in the drawing and described in the accompanying specification, it will be understood that the invention is not limited to such specific embodiment but is capable of modification, rearrangement and substitution of parts and elements without departing from the spirit of-the invention and within the scope of the appended claims.

What is claimed is:

1. In a telegraph transmitter, in combination, means for generating a signal including stop pulses and code pulse combinations, a transmission circuit, circuit means for applying said stop pulses and said code pulse combinations to said transmission circuit, switching means connected to suppress said stop pulses, and a switch actuator responsive to a characteristic of said signal for actuating said switching means to suppress said stop pulses.

2. In transmitting apparatus of a communication system, in combination, a transmissioncircuit, means for generating a signal including marking stop pulses and marking and spacing code pulses, a first circuit for applying said code pulses to said transmission circuit, a second circuit for applying said stop pulses to said transmission circuit, a switch connected to suppress said stop pulses when in a first position and to allow said stop pulses to be transmitted when in a second position, means for moving said switch to said first position, an actuator for said switch having a timing characteristic, and means for applying said marking and spacing code pulses to said actuator for energizing same, said actuator being adapted to move said switch to said second position upon being energized by a marking code pulse and to prevent movement of said switch to said first position for a definite period of time following each said marking code pulse.

3. A suppressor of stop pulses in a telegraph transmitter including a transmission circuit and a distributor having a stop segment, a start segment and code segments, said suppressor comprising a slow-release relay having an armature and a front contact in series with said stop segment and said transmission circuit, circuit means in series with said code segments, and means responsive to current in said circuit means for energizing the winding of said relay, said relay having a release timer greater than the greatest interval normally occurring between marking pulses from said code segments during ordinary transmission, whereby blank code combinations release said relay, thereby opening the circuit between said stop segment and said transmission circuit, to cause a long break to be transmitted.

4. A suppressor according to claim 3 including control means for starting and stopping said distributor, and means responsive to said control means for connecting said stop segment to said 17 a sm s n iresii e ai d stractss stopped. h

-1 l sr gh ansm tt r, n sss biea iea means n ti a s tes! in lu ng markin e s a d m rkin and spades cede p es a ns on c cu t sirt for ana -v.1 a said p u se s d was p lses is said ransmi s on s r t swi ch ng means ses esisd osu p e s said step Pu ses a witsh actua ia and means 9rei2i2ivie'ssa1d cede uls s is aid switch ac u tor an s h actua or pensive to the repetition iregu ency or" sa d p u ing code pulses adapted to actuate said switching means in a direction to suppress said stop pulses when the timeinterval between marking code pulses exceeds a predetermined value.

6. In a start-stop telegraph system, a transmission circuit, a transmitter having a plurality of output terminals and adapted to generate stop pulses at a first of said terminals and code pulse combinations including the blank combination at a second of said terminals, a stop pulse output circuit connecting said first terminal to said transmission circuit, a code pulse output circuit connecting said second terminal to said transmission circuit, and a timer adapted to suppress said stop pulses by opening said stop pulse output circuit at a control point, said timer being responsive to code pulses in said code pulse output circuit and being adapted to maintain said stop pulse output circuit closed at said control point only when marking code pulses are applied to said code pulse output circuit at repetition intervals less than the greatest interval between such pulses normally occurring during ordinary transmission of messages.

7. Apparatus as in claim 6 in which said timer comprises a slow-release relay having its armature and a front contact in series with said stop pulse output circuit.

8. Apparatus as in claim 7 including switching means capable of energizing said slow-release relay, and control means responsive to the operation of said transmitter adapted to control said switching means to energize said slow-release relay when said transmitter is stopped.

9. A suppressor of stop pulses in a telegraph transmitter of the type having a transmission circuit, means for generating stop pulses and combinations of code pulses, and means for applying said pulses to said transmission circuit, said suppressor comprising, in combination, switching means for suppressing the application of said stop pulses to said transmission circuit, an actuatortimer for actuating said switching means, and means for applying said code pulse combinations to said actuator-timer, said actuator-timer being responsive to repeated occurrences of a predetermined code pulse combination for actuating said switching means in a direction to suppress the application of said stop pulses to said transmission circuit.

10. In a telegraph system, a transmitter adapted to generate stop pulses and code pulse combinations including the blank combination, a stop pulse transmission circuit connected to receive stop pulses from said transmitter, switch means connected to suppress the transmission of stop pulses by said circuit, a code pulse transmission circuit connected to receive code pulse combinations from said transmitter, and means coupled to said code pulse transmission circuit adapted to actuate said switch mean in a direction to suppress said s'fip pulses in response to th said se 0nd terminal, l ss wi h, b s i branches and both said terminals, switch means for opening said transmission circuit at a point in series with said first terminal, and a control device of a timing type for controlling said switch means, said .device being responsive to code pulses in said second branch and being adapted to cause said switch means to open said transmission circuit upon the occurrence of a series of successive blank code combinations in said second branch.

13. In a telegraph transmitter, in combination, means for generating a signal including stop pulses and code pulse combinations, a transmission circuit, circuit means for applying said stop pulses and said code pulse combinations to said transmission circuit, switching means connected to interrupt said stop pulses, actuating means for said switching means, said actuating means comprising a wave shape discriminator, and means for applying at least a portion of said signal to said discriminator, said actuating means being adapted to actuate said switching means in one direction in response to one signal wave shape and in another direction in response to another signal wave shape, thereby controlling the transmission of said stop pulses.

14. In a start-stop telegraph system, a transmission circuit, a transmitter connected thereto, means in said transmitter for generating telegraph signal combinations including the blank code combination, relay means in said circuit energizable in response to the marking pulses of said combinations exclusive of the stop pulse, a circuit by-passing said relay means for impressing stop pulses on said transmission circuit, and a slow-release relay releasable by said relay means after the first blank code combination in any series of blank code combinations for interrupting said by-passing circuit to suppress the transmission of stop pulses and thereby efiect the transmission of a continuous break signal.

15. In a telegraph system having a plurality of interconnected stations, each of said stations having a printer-receiver, a motor for said printer-receiver, and a transmitter adapted to generate and transmit a signal including marking stop pulses and marking and spacing code pulse combinations, in combination at each of said stations, means at said receiver for stopping said motor in response to a long break signal, switching means at said transmitter, an actuator for said switching means, said switching means be ing connected to be capable of interrupting transmission of said stop pulses, and means for app1y ing to said actuator at least a portion of said generated signal including said code pulses, said actuator being adapted to actuate said switching means in a direction to interrupt said stop pulses upon receiving a definite number of successive spacing code pulses, said number being at least as great as the greatest number of successive spacing code pulses occurring during transmission of messages. a

16. In a telegraph tape transmitter, apparatus for transmitting a long break signal to a line in response to the receipt of blank tape [by said transmitter, said apparatus comprising, in combination, a rotary distributor including a brush arm,a start segment, a stop segment, and a plurality of code segments, said distributor being 'adapted to generate, each revolution, a'spacing start pulse andfa marking stop pulse, and to generateimarklng code pulses corresponding to any perforations inlthe tape and spacing code pulses corresponding to blank portions; of the tape; a circuit for transmitting stop pulses from normal said distributor to said line; a slow-release relay foropening said'circuit; means for transmitting marking and spacing code pulses from said distributor to said line;- and asecond relay responsive'to marking code pulses-passing throughsaid last-mentioned circuit, said second "relay being adapted to energize said slow-release relay upon the occurrence of amarking code" pulse, said slow-release relay having a release time at least equal to approximately the period of .onecomplete revolution of said distributor plus the interval required for said brush arm to travel from the end of the first code segment to the beginning of the last code segment. a

JOHN L.

No references cited. 

